Crystalline Gibbs Monolayers of DNA-Capped Nanoparticles at the Air–Liquid Interface

Abstract

Using grazing-incidence small-angle X-ray scattering in a special configuration (parallel SAXS, or parSAXS), we mapped the crystallization of DNA-capped nanoparticles across a sessile droplet, revealing the formation of crystalline Gibbs monolayers of DNA-capped nanoparticles at the air-liquid interface. We showed that the spatial crystallization can be regulated by adjusting both ionic strength and DNA sequence length and that a modified form of the Daoud-Cotton model could describe and predict the resulting changes in interparticle spacing. Gibbs monolayers at the air-liquid interface provide an ideal platform for the formation and study of equilibrium nanostructures and may afford exciting routes toward the design of programmable 2D plasmonic materials and metamaterials.

Crystallization of DNA‐Capped Gold Nanoparticles in High‐Concentration, Divalent Salt Environments

“…We used parallel small-angle x-ray scattering (parSAXS) which enabled us to uniquely probe the ordering phenomenon at the air-water interface independent of substrate effects. [10] Notably, our system is fully equilibrated (free particle exchange between bulk solution and Gibbs layer) and friction-free (in liquid rather than on a solid substrate). A droplet of polyT-DNA-capped AuNPs was deposited in a sealed chamber with a reservoir at the same salt concentration, in order to maintain equilibrium vapor pressure in the chamber and thus to stabilize the droplet volume and minimize far-from-equilibrium drying effects (see the Supporting Information).…”

“…A droplet of polyT-DNA-capped AuNPs was deposited in a sealed chamber with a reservoir at the same salt concentration, in order to maintain equilibrium vapor pressure in the chamber and thus to stabilize the droplet volume and minimize far-from-equilibrium drying effects (see the Supporting Information). [10] The scattering spectra at the interface of the droplet were captured in real time and in situ for non-base-pairing DNA-NPs across a range of ISs of monovalent NaCl and divalent MgCl 2 solutions.…”

“…[1][2][3][4][5][6] Correspondingly, investigations to elucidate the underlying mechanisms and interactions of soft nanoparticle crystallization have typically revolved around base-pairing DNA ligands, and thus within a limited range of ionic strengths (ISs) in monovalent salt solutions, so as to maintain the integrity of base-pairing. [1,2,[7][8][9][10] However, to transition into real-world applications, it is imperative to address the delicate balance in the crystallization of soft nanoparticles and biomolecules that make them extremely susceptible to instabilities leading to aggregation. A grand challenge in crystallization is tuning the underlying interactions that drive this multiparametric process.…”

Ionic depletion at the crystalline Gibbs layer of PEG-capped gold nanoparticle brushes at aqueous surfaces

“…In one approach, charged Langmuir monolayers have been used as templates that attract and crystallize capped nanoparticles from solutions [5][6][7]. In a different approach, it has been found that by manipulating salt concentrations in NPs suspensions, a Gibbs-like monolayer can be spontaneously formed and crystallized [8][9][10]. It should be emphasized that for all these assemblies, 2D or 3D, salts play a decisive role in tweaking the charge of the DNA strands and facilitate specific 3D assembly of NPs or migration of NPs to the liquid interface [5][6][7][8][9][10].…”

“…In a different approach, it has been found that by manipulating salt concentrations in NPs suspensions, a Gibbs-like monolayer can be spontaneously formed and crystallized [8][9][10]. It should be emphasized that for all these assemblies, 2D or 3D, salts play a decisive role in tweaking the charge of the DNA strands and facilitate specific 3D assembly of NPs or migration of NPs to the liquid interface [5][6][7][8][9][10]. In fact, a recent study suggests that the underlying mechanism that drives DNA-capped AuNPs to the surface and to crystallization has to do with the role of salt in tweaking the hydrophobic-hydrophilic character of the DNA-capped AuNPs [10].…”